Wireless communication device

ABSTRACT

A compact wireless communication includes a first radiating element and a second radiating element, which define and function as a dipole antenna, a feeder circuit including a wireless IC chip coupled with the first and second radiating elements, and a feeder substrate that is provided with the wireless IC chip. The first radiating element is provided to the feeder substrate. The second radiating element is provided to a substrate other than the feeder substrate.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to wireless communication devices andparticularly relates to wireless communication devices preferably use inradio frequency identification (RFID) systems.

2. Description of the Related Art

In recent years, as merchandise information management systems, RFIDsystems have been implemented in which communication using a non-contactmethod employing an electromagnetic field is performed between areader/writer that generates an induction magnetic field and an RFID tag(also referred to as a wireless communication device) attached to apiece of merchandise so as to transmit predetermined informationtherebetween. Such an RFID tag includes a wireless IC chip that storespredetermined information and processes a predetermined wireless signal,and an antenna that transmits and receives a high-frequency signal.

As an antenna used in such an RFID tag, dipole antennas such as thosedescribed in Japanese Unexamined Patent Application Publication No.2004-104344, Japanese Unexamined Patent Application Publication(Translation of PCT Application) No. 2009-524363 and InternationalPublication No. 2007-013168 are known. Dipole antennas can secure acomparatively large communication range, but have a problem in that theyhave a large size. In recent years, there has been a demand to “reduceRFID tags in size, despite this reducing the communication rangesomewhat”, but it has been difficult to respond to and satisfy thisdemand using conventional dipole antennas.

SUMMARY OF THE INVENTION

Accordingly, preferred embodiments of the present invention provide awireless communication device that includes two radiating elements thatdefine and function as a dipole antenna and is of a small size.

A wireless communication device according to a preferred embodiment ofthe present invention includes a first radiating element and a secondradiating element that define and function as a dipole antenna, a feedercircuit coupled with the first radiating element and the secondradiating element, and a feeder substrate that is provided with thefeeder circuit.

The first radiating element is provided to the feeder substrate.

The second radiating element is provided to a substrate other than thefeeder substrate.

A wireless communication device according to a second preferredembodiment of the present invention includes a first radiating elementand a second radiating element that define and function as a dipoleantenna, a feeder circuit coupled with the first radiating element andthe second radiating element, and a feeder substrate that is providedwith the feeder circuit.

The first radiating element is provided to the feeder substrate.

The feeder substrate includes a feeder terminal that is coupled with thesecond radiating element.

In the wireless communication devices of the first and second preferredembodiments of the present invention, the first radiating element andthe second radiating element are coupled with the feeder circuit so asto define and function as a dipole antenna, thus a requiredcommunication range is secured. The first radiating element is providedto the feeder substrate, which is provided with the feeder circuit, andis of a small size. Since the second radiating element is provided to asubstrate other than the feeder substrate in the first preferredembodiment or the feeder terminal of the feeder substrate is coupledwith the second radiating element in the second preferred embodiment,the second radiating element can have a large size compared to anothersubstrate having a large area, such as a motherboard. Therefore, themain portion of the wireless communication device including the feedersubstrate including the feeder circuit and the first radiating elementhas a small size.

With various preferred embodiments of the present invention, among thefirst radiating element and the second radiating element, which defineand function as a dipole antenna, the second radiating element isseparate from the wireless communication device and therefore thewireless communication device is reduced in size.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C illustrates a wireless communication device of a firstpreferred embodiment of the present invention, where FIG. 1A is aperspective view, FIG. 1B is a block diagram illustrating functions, andFIG. 1C is an equivalent circuit diagram.

FIGS. 2A and 2B illustrates the wireless communication device of thefirst preferred embodiment of the present invention, where FIG. 2A is aperspective view seen from the front side and FIG. 2B is a perspectiveview seen from the back side.

FIG. 3 is an exploded perspective view of the wireless communicationdevice of the first preferred embodiment of the present invention.

FIGS. 4A and 4B illustrate a wireless communication device of a secondpreferred embodiment, where FIG. 4A is a functional block diagram andFIG. 4B is an equivalent circuit diagram.

FIG. 5 is an equivalent circuit diagram of a wireless communicationdevice according to a third preferred embodiment of the presentinvention.

FIG. 6 is an exploded perspective view of a wireless communicationdevice of a fourth preferred embodiment of the present invention.

FIG. 7 is a sectional view of a wireless communication device of a fifthpreferred embodiment of the present invention.

FIG. 8 is a perspective view illustrating an example of mounting of awireless communication device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, preferred embodiments of a wireless communication deviceaccording to the present invention will be described with reference tothe accompanying drawings. In each of the drawings, components andelements that are the same as each other will be denoted by the samesymbols and repeated description thereof will be omitted.

A wireless communication device 1A according to a first preferredembodiment of the present invention is preferably used in a UHF-bandRFID system and as illustrated in FIGS. 1A-1C includes a first radiatingelement 11, a second radiating element 12, a wireless IC chip 20 thatdefines and functions as a feeder circuit, and a matching circuit 30.The first radiating element 11 and the matching circuit 30 are builtinto a feeder substrate 40 and the wireless IC chip 20 is mounted on thefeeder substrate 40. The wireless IC chip 20 has a function ofprocessing a high-frequency signal, preferably is a siliconsemiconductor integrated circuit chip, includes for example a clockcircuit, a logic circuit and a memory circuit, and stores necessaryinformation. The wireless IC chip 20 is coupled with the first radiatingelement 11 and is coupled with the second radiating element 12 via thematching circuit 30.

The matching circuit 30, as illustrated in FIG. 1C, defines a parallelresonance circuit including an inductor L1 and a capacitor C1 andachieves impedance matching between the wireless IC chip 20 and thesecond radiating element 12. A matching circuit may also be provided toachieve impedance matching between the wireless IC chip 20 and the firstradiating element 11.

The first radiating element 11, as illustrated in FIG. 1C, defines aseries resonance circuit including an inductor L2, a capacitor C2 and aninductor L3. The second radiating element 12 preferably has an elongatedshape over a comparatively wide area on a substrate other than thefeeder substrate 40, for example, on a printed wiring board 60 to beincorporated into a cellular phone. One end of the second radiatingelement 12 is connected to a feeder terminal 50 (refer to FIG. 3)provided on the back surface of the feeder substrate 40, which will bedescribed below, using solder or the like.

The feeder substrate 40, as illustrated in FIG. 3, is a multilayersubstrate formed preferably by stacking a plurality of dielectric layersor magnetic layers on top of one another. Connection electrodes 42 a to42 d are located on the front surface of a first layer 41 a, coilpatterns 43 and 44 and a capacitor pattern 45, which is connected to anend portion of the coil pattern 44, are located on the front surface ofa second layer 41 b, and capacitor patterns 46 and 47 are located on thefront surface of a third layer 41 c. In addition, a capacitor pattern 48and a coil pattern 49 are located on the front surface of a fourth layer41 d, and the feeder terminal 50 and an NC terminal 51 are formed on theback surface of the fourth layer 41 d.

The layers 41 a to 41 d are stacked on top of one another, and as aresult the connection electrode 42 a is connected to an end of the coilpattern 43 by a via hole conductor 52 a and is connected to thecapacitor pattern 46 by a via hole conductor 52 b. The connectionelectrode 42 b is connected to an end of the coil pattern 44 by a viahole conductor 52 c. In addition, the other end of the coil pattern 43is connected to the capacitor pattern 48 by via hole conductors 52 d and52 e. The capacitor pattern 47 is connected to an end of the coilpattern 49 by a via hole conductor 52 f. The capacitor pattern 48 isconnected to the feeder terminal 50 by a via hole conductor 52 g. The NCterminal 51 only faces the coil pattern 49 and an end portion of thecoil pattern 49 is not connected.

The coil pattern 43 defines the inductor L1, the coil pattern 44 definesthe inductor L2 and the coil pattern 49 defines the inductor L3. Theopposing capacitor patterns 46 and 48 define the capacitor C1 and theopposing capacitor patterns 45 and 47 define the capacitor C2.

Various ceramic materials can be used as the dielectric layers or themagnetic layers defining the feeder substrate 40 or resin materials maybe used. In the case where the feeder substrate 40 is formed of aceramic material, the conductor patterns provided on the individuallayers can be formed preferably by printing a conductive paste, forexample. In the case where the feeder substrate 40 is formed of a resinmaterial, the conductor patterns can be formed preferably by etching ametal foil or a metal film, for example.

That is, in this first preferred embodiment, the feeder substrate 40 isa multilayer substrate and the first radiating element 11 and thematching circuit 30 are built into the feeder substrate 40. However, itis not necessary for the all of the coil patterns to be built into thefeeder substrate 40.

The wireless IC chip 20 includes input/output electrodes 21 a and 21 b(refer to FIG. 1B) that receive a high-frequency signal as a potentialdifference. These input/output electrodes 21 a and 21 b are connected tothe connection electrodes 42 a and 42 b provided on the feeder substrate40 via solder bumps or the like, one input/output electrode 21 a isconnected to the first radiating element 11 (inductor L2), and the otherinput/output electrode 21 b is connected to the second radiating element12 via the matching circuit 30 (inductor L1, capacitor C1 and feederterminal 50).

In this wireless communication device 1A, the first radiating element 11and the second radiating element 12 are connected to the wireless ICchip 20 and function as a dipole antenna. When the distance is long,transmission and reception of high-frequency signals with areader/writer for an RFID system is performed by mainly utilizing thesecond radiating element 12. When the distance is short, transmissionand reception of high-frequency signals is performed by mainly utilizingthe first radiating element 11.

The first radiating element 11 is built into the feeder substrate 40 andthe second radiating element 12 is provided on the printed wiring board60, which is a substrate that is other than the feeder substrate 40.Therefore, the practical size of the wireless communication device 1A isthe size of the feeder substrate 40 and a reduction in size is achieved.In addition, the feeder substrate 40 is mounted on the second radiatingelement 12, but is only connected to the second radiating element viathe feeder terminal 50 (one place connection) and therefore thepositional accuracy required in mounting is relaxed.

Second Preferred Embodiment

In a wireless communication device 1B of a second preferred embodimentof the present invention, as illustrated in FIGS. 4A and 4B, theinput/output electrodes 21 a and 21 b of the wireless IC chip 20 areconnected to the matching circuit 30. The matching circuit 30 includesan inductor L4, in addition to the inductor L1 and the capacitor C1described in the first preferred embodiment. One input/output electrode21 a of the wireless IC chip 20 is connected to a connection pointbetween the inductors L4 and L2 and the other input/output electrode 21b is connected to a connection point between the inductor L4 and aparallel resonance circuit (inductor L1 and capacitor C1).

The rest of the configuration of the second preferred embodimentpreferably is the same or substantially the same as that of the firstpreferred embodiment and the operational effects are the same as thatdescribed in the first preferred embodiment. The inductor L4 added tothe matching circuit 30 defines and functions as an element that adjuststhe degree of coupling between the first radiating element 11 and thesecond radiating element 12.

Third Preferred Embodiment

In a wireless communication device 1C of a third preferred embodiment ofthe present invention, as illustrated in FIG. 5, the configuration ofthe matching circuit 30 is changed. The matching circuit 30 includes aseries resonance circuit including an inductor L5 and a capacitor C3 anda series resonance circuit including an inductor L6 and a capacitor C4,and these two resonance circuits are connected to each other via aninductor L7. The inductors L5 and L6 are wound in opposite directions,are arranged adjacent to each other, and are electromagnetically coupledwith each other. In addition, the inductor L4 that adjusts the degree ofcoupling described in the second preferred embodiment is connectedbetween the first radiating element 11 and the feeder terminal 50.

One input/output electrode 21 a of the wireless IC chip is connected toone end of the inductor L6 and the other input/output electrode 21 b isconnected to one end of the inductor L5. In addition, a connection pointbetween the capacitor C4 and the inductor L4 is connected to the firstradiating element 11 (inductor L2) and a connection point between thecapacitor C3 and the inductor L4 is connected to the second radiatingelement 12 via the feeder terminal 50.

The rest of the configuration of the third preferred embodimentpreferably is the same or substantially the same as that of the firstpreferred embodiment and the operational effects are the same as thatdescribed in the first preferred embodiment. In the matching circuit 30,the first and second radiating elements 11 and 12 operate at thedifferent resonant frequencies possessed by the two series resonancecircuits and as a result the communication band is widened. In addition,this preferred embodiment is the same as the second preferred embodimentin the point that the inductor L4 adjusts the degree of coupling betweenthe first radiating element 11 and the second radiating element 12. Theinductor L7 matches an impedance of the feeder terminal.

Fourth Preferred Embodiment

In a wireless communication device 1D of a fourth preferred embodimentof the present invention, as illustrated in FIG. 6, the feeder terminal50 is built into the lowermost layer of the feeder substrate 40 and theback surface of the feeder substrate 40 is adhered to the secondradiating element 12 so as to couple the feeder terminal 50 and thesecond radiating element 12 with each other through a capacitor C5. Thefeeder terminal 50 is located on the front surface of the fifth layer 41e of the feeder substrate 40. The rest of the configuration of thefeeder substrate 40 illustrated in FIG. 6 preferably is the same orsubstantially the same as that illustrated in FIG. 3.

In this fourth preferred embodiment, except the matching circuit 30 andthe second radiating element 12 being coupled with each other throughthe capacitor C5, the configuration preferably is the same orsubstantially the same as that of the first preferred embodiment.Therefore, the operational effects of the fourth preferred embodimentare substantially the same as that of the first preferred embodiment,but in particular the anti-surge performance is improved by thecapacitor C5.

Fifth Preferred Embodiment

In a wireless communication device 1E of a fifth preferred embodiment ofthe present invention, as illustrated in FIG. 7, the wireless IC chip 20is arranged in a center portion of the feeder substrate 40, whichincludes multiple layers, the first radiating element 11 is arranged ina top portion, and the matching circuit 30 is arranged in a bottomportion. The wireless communication device 1E is adhered to the printedwiring board 60 with adhesive layers 62. An equivalent circuit of thispreferred embodiment is preferably the same as that of the firstpreferred embodiment illustrated in FIG. 1C. Therefore, the operationaleffects of the fifth preferred embodiment are substantially the same asthat of the first preferred embodiment. In particular, in the fifthpreferred embodiment, the first radiating element 11 is arranged on thefront surface side of the feeder substrate 40 and thereforecommunication performance is improved when the antenna of areader/writer is brought closer to the wireless communication device 1E.In addition, the wireless IC chip 20 is interposed between the matchingcircuit 30 and the first radiating element 11, and as a result isolationof the matching circuit 30 and the first radiating element 11 from eachother is improved. In the sectional view of FIG. 7, illustration ofhatching is omitted so as to avoid complexity. The electrode 51 is formounting the feeder substrate 40, but even if omitted, the wirelesscommunication device 1E would still function as an RFID tag. In thiscase, the electrode (feeder terminal) 50 can be made larger and thepositional accuracy required in mounting is relaxed.

The wireless communication devices 1A to 1E of the preferred embodimentshave been described as preferably being mounted on the printed wiringboard 60. However, other than this, the wireless communication devicecan be mounted on a variety of pieces of merchandise or on the packagingof a piece of merchandise. In FIG. 8, the wireless communication device1A is illustrated as being mounted on a packaging bag 70 of a foodproduct. The packaging bag 70 has aluminum vapor deposited over itsentire surface and the wireless communication device 1A is affixed to anedge portion, which is a seam portion 71, of an aluminum vapor depositedfilm 72 (functioning as the second radiating element).

Other Preferred Embodiments

Wireless communication devices according to the present invention arenot limited to the above-described preferred embodiments and can bemodified in various ways within the scope of the gist of the presentinvention.

In particular, the first radiating element and the matching circuit caninclude a variety of circuit elements and are not limited to circuitconfigurations including inductors and capacitors as described in thepreferred embodiments. The second radiating element can have a varietyof shapes such as a meandering shape and a coil shape, for example. Inaddition, coupling of the first and second radiating elements and thewireless IC chip may be any of magnetic field coupling, capacitivecoupling, electric field coupling, electromagnetic field coupling anddirect current coupling.

The wireless IC chip may include four input/output electrodes so as tobe suitable for use with two dipole antennas. In addition, the feedersubstrate may take the form of a separate substrate as a standalone unitor a rewiring layer to connect a terminal provided on a mounting surfaceof a wireless IC chip may double as the substrate.

As described above, preferred embodiments of the present invention canbe used in wireless communication devices and are particularly excellentin that a wireless communication device can be reduced in size.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

1. (canceled)
 2. A piece of merchandise including a wirelesscommunication device, comprising: a feeder substrate including awireless IC chip, a first radiating element connected to the wireless ICchip, and a feeder terminal of a feeder circuit connected to thewireless IC chip; and a packaging bag including a second radiatingelement; wherein the feeder substrate is attached to the packaging bag,and the feeder terminal of the feeder circuit is connected to the secondradiating element of the packaging bag via capacitive coupling.
 3. Apiece of merchandise including a wireless communication device accordingto claim 2, wherein the feeder substrate is attached to an edge portionof the packaging bag so that the first radiating element does notoverlap with the second radiating element when viewed in a plane in adirection perpendicular to a principal surface of the feeder substrate.4. A piece of merchandise including a wireless communication deviceaccording to claim 2, wherein the feeder substrate includes aninductance element that defines a matching circuit.
 5. A piece ofmerchandise including a wireless communication device according to claim4, wherein the wireless IC chip includes first and second input/outputelectrodes, and the inductance element defining the matching circuit isconnected between the first and second input/output electrodes.
 6. Apiece of merchandise including a wireless communication device accordingto claim 2, wherein the wireless IC chip processes a high-frequencysignal in a UHF-band.
 7. A piece of merchandise including a wirelesscommunication device according to claim 2, wherein the second radiatingelement of the packaging bag is an aluminum vapor deposited film.